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Full text of "Handbook Of Chemical Engineering - I"

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The Problem.—The transportation of solids by mechanical or semi-mechanical means resolves itself into an economic question in which the three dominant factors are: (1) Material, its characteristics and the quantity to be transported; (2) speed, or time consumed in the operation; and (3) equipment and operation costs. The material to be handled is a known quantity and the time consumed in the operation is subject to close regulation by employing equipment of suitable capacity operated at its most effective speed for handling the class of material, so the handling equipment proper to employ is dependent upon the cost of the equipment and the gross expense entailed in its operation—the net operating cost. No fixed rules can be advanced or definite recommendations made as to the best type of equipment to employ, for rarely are the controlling factors the same in even similar handling problems.
Distinguished from general transportation, which embraces the questions of rail, water and motor-truck transportation over long distances, material handling in the present chapter will be confined to the economic transportation of materials in and about the industrial plant or mine and over comparatively short distances—the conveying and elevating of material by the assistance of mechanical aids.
Classification of Equipment.—Equipment for the mechanical handling of materials may be classified as the carriers which carry the material in a limited but continuous stream (endless conveyors and elevators), and the hoists, trucks and railways which carry more concentrated, and frequently more compact, loads more or less intermittently. This classification will be adhered to so far as practical to simplify a logical selection of handling equipment for the industrial establishment and consideration of equipment will parallel the passage of the material, commencing with its delivery.
Economic Comparisons.—Power being required to operate practically all types of conveying and elevating machinery, the power consumption in horsepower or kilowatts per hour as well as the initial and gross operating costs of the equipment will serve as the basis of economic measurement, the relative net cost of operation being then a simple matter of comparison between suitable systems of transportation.
Characteristics.—Self-propelling, mobile cranes of the locomotive type are ordinarily mounted on standard-gage trucks with four or eight wheels, and equipped with a hoisting boom carrying a clam-shell or orange-peel bucket, shovel or electric magnet, depending upon the nature of the service to be ren-
1 Engineering Economist, Montclair, N. J.